The invention relates to compositions, methods, and apparatuses for reducing the release of malodorous sulfide gases from water sources. Sulfide gases such as but not limited to DMDS and hydrogen sulfide are malodorous gases whose presence in populated areas are often perceived of as an irritating nuisance. In addition sulfide gases can be explosive, corrosive, and hazardous to health. Most pernicious of all, prolonged contact to sulfide gases can anesthetize one's sense of smell causing the loss of one's ability to detect the presence of other more toxic gases.
This problem is particularly acute when dealing with expelled water from the food processing industry. The food processing industry employs vast quantities of water to create purified food products. Among the food industries with high volumes of water requirements are the sugar cane processing, sugar beet processing, fruit and vegetable processing, meat and poultry processing, grain processing, fat and oil processing, and dairy product processing industries. Unit operations that are most common to the various types of food processing listed above include energy transfer systems, including boiler systems.
In food industries such as the sugar industry, the condensate released by a multiple effect evaporator (“MEE”) is an example of a typical expelled fluid. MEE often becomes contaminated and must be disposed of as wastewater. Examples of these contaminating events include steam carry-over, foaming induced by MEE control issues, leaking of sugar thin juice into the stream, or other causes. Contamination is generally comprised of organic salts, inorganic salts, and sucrose. These events are more likely to happen during operation upsets and can cause “sugar shot” (a sudden spike in sugar dosage/concentration in the process fluid). Sugar shots pose particular problems with wastewater disposal as they result in wild variations in microorganisms' populations, diversity, activity, and waste processing capabilities. These wild variations complicate the process of odor management in wastewater.
Unfortunately as described for example in U.S. Pat. No. 7,160,712, malodorous sulfide gases are a common byproduct of waste water treatment. In wastewater treatment microorganisms are used to break down organic (waste) material. Microorganisms accomplish this by utilizing oxygen to oxidize the material as a part of their metabolic functions. Because of its efficiency in microorganism's metabolisms, when available, microorganisms will preferably utilize aerobic processes which require molecular oxygen. When molecular oxygen is less than optimally available, some microorganisms will use anaerobic processes which use other compounds such as nitrates and sulfates. Because nitrates afford superior metabolic efficiency when compared to sulfates, organisms will only use sulfates for oxidation when both nitrates and molecular oxygen are less than optimally available. Sulfate oxidation produces sulfide gases.
Not all organisms are capable or are as capable of utilizing sulfates to metabolize organic material. Organisms that are highly effective at oxidizing or reducing sulfur bearing species (such as sulfates, thiosulfates, and elemental sulfur) are known as SRP (sulfur reducing prokaryotes). A profusion of SRP in a water sample will often result in high releases of sulfide gases. In addition, as SRP proliferate, they tend to strip water supplies of all their oxygen content resulting in highly anaerobic conditions. Once the water becomes anaerobic, the ability of microorganisms to break down organic material drastically slows. As a result a number of legal jurisdictions prohibit the discharge of treated water that contains too little dissolved oxygen. Thus SRP profusion is both a nuisance and makes water disposal difficult.
A number of prior art strategies have been proposed to address the release of sulfide gas. One approach is sulfide scavenging. In sulfide scavenging chemicals are applied to the water which reacts with and traps the sulfide gas before it vaporizes out of the liquid medium. As described in Published US Patent Applications 2012/0012507, 2012/0012506, 2012/0329930, 2012/0067782, 2009/0242461, and European Patent Application EP 0 882 778 A2, scavengers include but are not limited to chlorine, bleach, hydrogen peroxide, potassium permanganate, ferric chloride, hydrogen sulfide, glyoxal, glyoxal-polyamines, alpha-amino ethers, polyaliphatic amines, alkyl-triazines, and nitroxides. Another strategy is sulfate substitution which involves feeding molecular oxygen or nitrates into the water to displace sulfates from being metabolized. And a third strategy as described in U.S. Pat. No. 6,015,536 is to treat the gaseous effluent itself to remove the sulfides.
Unfortunately all of these prior approaches are excessively complex, costly, unreliable, and/or are otherwise unsatisfactory. As a result there remains a clear utility in improved compositions, methods, and apparatuses for reducing the release of malodorous sulfide gases from water sources. The art described in this section is not intended to constitute an admission that any patent, publication or other information referred to herein is “prior art” with respect to this invention, unless specifically designated as such. In addition, this section should not be construed to mean that a search has been made or that no other pertinent information as defined in 37 CFR § 1.56(a) exists.